Neuroactive steroids act in the peripheral nervous system as physiological regulators and as protective agents for acquired or inherited peripheral neuropathy. In recent years, modulation of neuroactive steroids levels has been studied as a potential therapeutic approach to protect peripheral nerves from damage induced by diabetes. Nuclear receptors of the liver X receptor (LXR) family regulate adrenal steroidogenesis via their ability to control cholesterol homeostasis. Here we show that rat sciatic nerve expresses both LRX␣ and  isoforms and that these receptors are functional. Activation of liver X receptors using a synthetic ligand results in increased levels of neurosteroids and protection of the sciatic nerve from neuropathy induced by diabetes. LXR ligand treatment of streptozotocin-treated rats increases expression in the sciatic nerve of steroidogenic acute regulatory protein (a molecule involved in the transfer of cholesterol into mitochondria), of the enzyme P450scc (responsible for conversion of cholesterol into pregnenolone), of 5␣-reductase (an enzyme involved in the generation of neuroactive steroids) and of classical LXR targets involved in cholesterol efflux, such as ABCA1 and ABCG1. These effects were associated with increased levels of neuroactive steroids (e.g., pregnenolone, progesterone, dihydroprogesterone and 3␣-diol) in the sciatic nerve, and with neuroprotective effects on thermal nociceptive activity, nerve conduction velocity, and Na ϩ , K ϩ -ATPase activity. These results suggest that LXR activation may represent a new pharmacological avenue to increase local neuroactive steroid levels that exert neuroprotective effects in diabetic neuropathy.
Different, yet compatible: A hybrid capsule is formed through hydrogen bonding between two different subunits, each of which is capable of self‐assembly into homodimeric capsules. The hybrid forms in response to a guest that fills its space properly. Formation of the molecular capsule (see picture) is supported by 1H NMR spectroscopy experiments.
The synthesis of several amphiphilic, nonpeptidic scaffolds that mimic the presentation of i, i + 3 or i + 4, and i + 7 residues of a peptide alpha-helix is described. The approach uses a pyridazine core, and the synthesis involves only a few steps and minimizes the number of C-C bond-forming reactions. The versatility of the synthesis makes it suitable for the preparation of small libraries of low molecular weight alpha-helix mimetics that could be targeted to certain protein/protein interactions.
Diabetic peripheral neuropathy (DPN) appears frequently in patients diagnosed with type 1 or type 2 diabetes ( 1-3 ). The extent of abnormalities is more pronounced if the hyperglycemia is not controlled properly ( 4, 5 ). DPN is associated with deleterious changes in peripheral nerves, such as myelin damage and decrease in nerve conduction velocity ( 4-9 ). Similar structural abnormalities and neurophysiological changes have been observed in the peripheral nerves of streptozotocin (STZ)-treated rats, an experimental model that captures many features of type 1 diabetes ( 10-12 ). As it is seen in diabetic subjects, STZtreated rats show increased morphological alterations in the myelinated fi bers of the sciatic nerve ( 13 ).Abstract Diabetic peripheral neuropathy (DPN) is characterized by myelin abnormalities; however, the molecular mechanisms underlying such defi cits remain obscure. To uncover the effects of diabetes on myelin alterations, we have analyzed myelin composition. In a streptozotocintreated rat model of diabetic neuropathy, analysis of sciatic nerve myelin lipids revealed that diabetes alters myelin's phospholipid, FA, and cholesterol content in a pattern that can modify membrane fl uidity. Reduced expression of relevant genes in the FA biosynthetic pathway and decreased levels of the transcriptionally active form of the lipogenic factor sterol-regulatory element binding factor-1c (SREBF-1c) were found in diabetic sciatic nerve. Expression of myelin's major protein, myelin protein zero (P0), was also suppressed by diabetes. In addition, we confi rmed that diabetes induces sciatic nerve myelin abnormalities, primarily infoldings that have previously been associated with altered membrane fl uidity. In a diabetic setting, synthetic activator of the nuclear receptor liver X receptor (LXR) increased SREBF-1c function and restored myelin lipid species and P0 expression levels to normal. These LXR-modulated improvements were associated with restored myelin structure in sciatic nerve and enhanced performance in functional tests such as thermal nociceptive threshold and nerve conduction velocity. These fi ndings demonstrate an important role for the LXR-SREBF-1c axis in protection from diabetes-induced myelin abnormalities .-
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